Paddy fields are regarded as an important anthropogenic source of atmospheric CH4 and play a significant role in global warming. Biochar refers to the highly aromatic substance remaining after thermal decomposition of biomass under complete or partial exclusion of oxygen for the purpose of creating a soil amendment. Its application is widely accepted to be a promising method to decrease CH4 emission from paddy soil. The balance between CH4 production and consumption ultimately determines whether a paddy soil is a net source or a sink of atmospheric CH4. However, there are few studies concerning the effects of biochar amendments on methanogenic and methane oxidation activities in paddy soils. Meanwhile, the feedstock used for biochar production has a substantial impact on the physiochemical characteristics of biochar. These characteristics are then related to the actual environmental function in soil, such as response to methanogenic and methane oxidation activities. In this study, a one-year field experiment was conducted to gain insight into the potential effects of bamboo biochar (BB) and rice straw biochar (SB) amendments at the rate of 22.5 t/hm2 on the methanogenic and methane oxidation activities in rice rhizosphere soil. The SB had more hydrophilic groups such as carboxyl and hydroxyl, higher pH and electrical conductivity (EC) values and lower bulk density than the BB did. Soil water content, pH, and EC values in the SB treatments were greater than those in the BB treatments. Generally, urea application did not have notable impact on soil water content, pH and EC values. Compared with the control treatment, methanogenic activitiy in the rhizosphere soil at the rice seedling stage was significantly increased with the SB amendment. There was no significant difference in the methanogenic activity between the control and the BB treatments during the whole period of rice growth. Differences in the labile components and ash contents between the two biochars may have resulted in the divergence of methanogenic microorganisms in the rice rhizosphere soil, and consequently the difference in methanogenic activity between the BB and SB treatments. The methane oxidation activity in the rhizosphere soil increased with the addition of BB and SB during the rice growth period. Nevertheless, statistical analysis indicated that significant differences were only observed in the SB treatment at the seedling and maturing stages of rice development. In comparison with the BB treatment, SB application was more effective in increase of soil pH and EC values, soil K and P contents, and soil aeration, which may have contributed to the significant improvement of methane oxidation activity in rhizosphere soil with SB application. The general trends of biochar impact on methanogenic and methane oxidation activities were not observably changed with urea application. In conclusion, SB could be used to reduce paddy soil CH4 emission through increasing soil methane oxidation activity.% 为了揭示生物质炭输入对稻田根际土壤产甲烷和甲烷氧化活性的影响，该文通过1a 的田间试验，研究了2种原料制备的生物质炭（竹炭和水稻秸秆炭）对水稻根际土壤产甲烷和甲烷氧化活性的影响。结果表明，2种生物质炭因理化性质的不同，对水稻根际土壤产甲烷活性和甲烷氧化活性的影响存在较大差别。秸秆炭的输入可以显著提高水稻苗期根际土壤产甲烷活性，而竹炭在水稻的整个生长期对根际土壤产甲烷活性均没有显著性影响。竹炭和秸秆炭不稳定易降解组分含量的差异，使其对稻田土壤产甲烷微生物产生不同程度的影响，进而导致稻田根际土壤产甲烷活性响应差别。除抽穗期竹炭处理和成熟期秸秆炭处理，尿素施加并未显著改变生物质炭对根际土壤产甲烷活性的影响趋势。在水稻整个生长期，秸秆炭和竹炭对稻田土壤甲烷氧化活性都有促进作用，但只有秸秆炭在苗期和成熟期表现出显著性的差异。尿素对苗期和抽穗期根际土壤甲烷氧化活性有促进作用。与竹炭相比，秸秆炭输入在改善土壤通气条件、提高土壤pH值和电导率EC、以及K、P元素含量等方面更为有效，同时可能是秸秆炭对水稻根际土壤甲烷氧化活性产生显著性促进作用的潜在机理。
展开▼
